restlet get is not sending done confirmation - http

Question

Hi I have a simple restlet get method which returns a static string. It looks like the following:
#Get
public String represent() {
return "mystring\r\n";
}
A low level c app is invoking this get by going into a read loop. It never receives a finish confirmation signaling it that there is no more data left to read and times out after 20 seconds. Is there code I need to send to alert the client app that no more data is coming? Or that the get is finished?

Answer 1

[Note: The code written below is partly based on the samples available on http://www.restlet.org ]
HTTP 1.0 and 1.1 have a header named Content-Length. Whatever is the numeric value of that header, is the length of the body of the HTTP-response. Going a step further in HTTP 1.1, there is another header name-value, Tranfer-Encoding: chunked which indicates that the response-body is divided into parts (chunks) and each part's length is mentioned in a line just before that part is delivered.(I am not including other values of Transfer-Encoding to keep this answer concised.)
If this is my restlet server:
package restletapp;
import org.restlet.Component;
import org.restlet.data.Protocol;
import org.restlet.resource.Get;
import org.restlet.resource.ServerResource;
public class RestletApp extends ServerResource {
public static void main(String[] args) throws Exception {
Component component = new Component();
component.getServers().add(Protocol.HTTP, 8182);
component.getDefaultHost().attach("/trace", RestletApp.class);
component.start();
}
#Get
public String toAtGet() {
return "Resource URI : " + getReference() + '\n'
+ "Root URI : " + getRootRef() + '\n'
+ "Routed part : " + getReference().getBaseRef() + '\n'
+ "Remaining part: " + getReference().getRemainingPart()
;
}
}
And this is my client (written using Sockets in Java. Just sends a minimal HTTP request, and prints each character of response on console.)
package restletapp;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.net.Socket;
import java.net.UnknownHostException;
public class Requester {
public static void main(String[] args) throws UnknownHostException, IOException {
Socket s=new Socket("localhost", 8182);
OutputStream os = s.getOutputStream();
os.write((
"GET /trace HTTP/1.1\r\n" //request
+ "host: localhost:8182\r\n" //request
+ "Connection-type: close\r\n\r\n" //request
).getBytes());
InputStream is = s.getInputStream();
for(int ch;(ch=is.read())!=-1;System.out.flush())
System.out.write(ch); //response, one char at a time.
is.close();
os.close();
s.close();
}
}
The client process never ends. But if I change my client program to this:
package restletapp;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.net.Socket;
import java.net.UnknownHostException;
public class Requester {
public static void main(String[] args) throws UnknownHostException, IOException {
Socket s=new Socket("localhost", 8182);
OutputStream os = s.getOutputStream();
os.write((
"GET /trace HTTP/1.1\r\n"
+ "host: localhost:8182\r\n"
+ "Connection-type: close\r\n\r\n"
).getBytes());
InputStream is = s.getInputStream();
BufferedReader br = new BufferedReader(new InputStreamReader(is));
int bytesRead=0;
int contentLength=0;
//response headers.
for(String line;!(line=br.readLine()).isEmpty();System.out.flush()){
System.out.println(line);
String[] tokens = line.split(":| ");
if(tokens[0].equalsIgnoreCase("content-length")){
contentLength=Integer.parseInt(tokens[2]);
}
}
//response separator, between headers and body.
System.out.println();
//response body.
while(bytesRead<contentLength){
System.out.write(br.read());
System.out.flush();
bytesRead++;
}
is.close();
os.close();
s.close();
}
}
In the second version of Requester, you can see that the connection is closed by the client when response body's content-length-number of characters are read.
This is what i get using curl:
command line $ curl -i "http://localhost:8182/trace"
HTTP/1.1 200 OK
Date: Fri, 14 Jun 2013 11:54:32 GMT
Server: Restlet-Framework/2.0.15
Vary: Accept-Charset, Accept-Encoding, Accept-Language, Accept
Content-Length: 148
Content-Type: text/plain; charset=UTF-8
Resource URI : http://localhost:8182/trace
Root URI : http://localhost:8182/trace
Routed part : http://localhost:8182/trace
Remaining part:
command line $
You can see, that curl exits after reading the content.